Shipping container refrigerated by dry ice



Patented 7, -1948 UNITED STATES PATENT OFFICE SHIPPING CGNTAINERBEFBIGEBATED BY DRY ICE Andrew J. Nicholas, North HavenQConn., assignorto The Grenby Manufacturin r Company,

Plainvilie, Conn., a corporation of Connecticut Application May 2s,194s, serial No. msu

.(ci. ca -91.5)

ll Clllml.

The present invention relates to refrigeration and more particularly toa refrigerating unit uti" lizing solidifiedA carbon dioxide or itsequivalent as a primary refrigerant. which unit is admirably adapted touse in a portable refrigerator in the nature of a refrigerated shipping.container. There is definite utility for a shipping 'container of4modertae size which may be handled very much as' any ordinary containeroi' equivalent size but which container comprises a portablerefrigerator. In particular. -such a refrgierated 2 erated space as tocause positive circulation Aof the'atmosphereinsuch space. l ",It is afurther object of thepresent invention to' provide a portablerefrigerator having a loadcai'ryin'g compartment into which aooinirioliity*v needing refrigeration may be placed and a read-- ilyremovable reirigerating unit which may .be inserted into therefrigerator and removed thereshipping container is of great value inproviding for refrigerated shipment of relatively small quantities ofperishable materials from scattered temperature.- For example, thetemperatre of .y

solidified CO2 is -108 F.- and such temperature is of courseincompatible with such perishable commodities as fresh-vegetables andthe like.

It is a. further object of the prsent invention to provide arefrigerating-unitutilizing solidied CO2 as a primary refrigerant andwhich Willoperate to maintain adesired moderately cooll temperaturewithout moving parts or mechanical regulating devices.

It is a further object of the present invention to provide arefrigerating unit of the type described which will operate for periodsof time sufficient to permit relatively long distance shipment of arefrigerated commodity without the necessity for recharging' orservicing of the re f rigerating unit. l f

It is a'. further object of the present invention to provide .arefrigerating unit whichutilizes solidied G02 as a primary refrigerantand which utlizes a. liquid' secondary refrigerant having apredetermined freezing point and to provide for heat exchange betweenevaporated gaseous CO2 and the secondary refrigerant.

It is a further object of the present invention to provide a.refrigerating unit as set forth in the next preceding object in whichthe gaseous CO: isI conducted after heat-exchange with the secondaryrefrigerant to such a point in the refrigfrom for serviclngyrecharging*or replacement Without disturbing the commodity.'

4It is a further object of the-present invention.

to'provide a refrigerated shipping container adapted to receive a loadof material' needing reff frlgeration and which is provided witha'readily removable refrigerating unit solidified CO2 asf a primary'refrigerant and which may be replaced or recharged along thelineof'shipment.'

Other and further objects of the present invention will becomehpvparentIfrom a consideration of the following detailed description' of apreferred form of the invention taken in connection with the drawings.accompanying `and forming a part of this specification.

25. In the drawing the gure is a sectional view of a refrigerator madein accordance with the present invention. f

Referring' now to the drawing. there is shown a refrigerator. comprisinga cabinet i0 having afood storage or load-carrying'l compartment l2 andone or more movable closures Il providing access to the compartment It..The refrigerator also comprises a refrigerating unit indicated generallyat I6 which isl insertable into the body of the cabinet through anOpening of suitable size which is closed by a movable closure Il. Itisto be understood that the cabinet :il may have any suitable shape.`The .form illustrated is generally rectangular in shape. having endwalls 20, front and back walls 22. only one of which is shown ,inthedrawing, a bottom wall 24 and a top wall Il. Each 0f the Walls 2l,22, I L'and 2| as well.

. ATheopening '62 which is closed by'theclosure I6 is preferably squarein shape. 'I'his openingV tical edges to the front and rear walls 22 asbyy brackets 46. This foraminous enclosure thus is preferably apermanent part of'the refrigerator cabinet and serves to prevent directcontact between the perishable commodity stored therein and therefrigerating unit I6. Furthermore, the provision of such an enclosureassures that the refrigerating unit I6 may be removed and replacedwithout disturbing the load within the cabinet. It will be understoodthat the foraminous en- 'closure need only be slightly larger than therefrigerating unit I6, and that in the event the cabinet I6 is soproportioned as to be considerably wider'in a direction perpendicular tothe plane of the sectional view of the drawing than is the unit I6, theforaminous enclosure may take the form of a basket closed on all foursides by screen or other suitable material similar to the panels 66.

The refrigerating unit I6 comprises upper and lower rigidly connectedcontainers 42 and 44, respectively, which willbe described in greaterdetail herein below. The upper container 42 is provided with elongatedangles 46 secured adjacent all four upper edges thereof, thehorizontally extending flanges 46 of which rest upon the flanges 66within the opening 32. The refrigerating unit i6 is thus supported onall four. sides merely by resting upon the flanges 36 and the unit maythus be readily lifted from the refrigerator when the closure i6 isopened.

The refrigerating unit I6 will now be described in detail. The uppercontainer 42 is adapted to receive a block 50 of solidified CO2.Preferably, the container 42 is provided with an inner basket l2 made ofscreen or other suitable foraminous material which serves to keep thesolidified CO2 out of direct contact with the walls of the container 42.

The container 42 is preferably made of metal and is adapted to be closedin a substantially gastight manner. To this end, there may be provided agasket '54 made of rubber or other suitable material extending aroundthe upper operi end of the container 42. A closure 56 is provided torest upon the gasket 64 and may be drawn tightly into place by asuitable number of screws 66 provided around the margins of the closure66. The screws 56 may be threadably received in fixed nuts 60 providedwithin the angles 46. Preferably, the gasket 54 is relatively thick andsoft in order to provide not only for sealing of the container 42 undernormal conditions, b ut also to permit escape of gas therearound in theevent a dangerous pressure is developed within the container 42. Ahandle 62 may be secured to the closure 66 to facilitate lifting of theunit i6 and removal of the closure 66 from the unit when desired.

The lower container 44 is preferably supported by the upper container42and is spaced therefrom in order to provide substantially no direct heattransfer between the two containers 42 and uid in operation of thedevice.

44. To this end a plurality yoi' angle brackets 64 are-secured as bywelding to the lower exterior surface of the upper container 42. Thebrackets,E 64 are spaced from one another as faras practicable, havingdue regard to strength re quirements. the brackets 64 extend outwardlybeyond the exterior surfaces of the vertical walls of the uppercontainer 42 and thus the vertically disposed arms of the brackets 64are spaced outwardly from such vertical surfaces. An intermediatecontainer 66 is secured to the outer vertical surfaces of the brackets64 and this intermediate container comprises four vertical walls 66which extend hori- Izontally beyond the upper container 42 and arelatively narrow shelf-like bottom 10 extending around all four sidesthereof. The bottom 'I6 is formed with downwardly turned flanges 12which are in turn secured to the exterior surfaces of the lowercontainer 44 and thus serve to support the same.

The intermediate container 66 is open ati-ts y top all the way aroundthe upper container 42, such opening existing between the angle brackets64 and within the space between the walls 66 of the intermediatecontainer and the vertical walls of the upper container 42. Theintermediate container 66 is thus positioned to catch water from meltingfrost on the surfaces of the upper container 42 and to hold suchaccumulated moisture until such time as it may be removed by operationof a suitable pet cock 14.

The lower container 44 is provided for a liquid secondary refrigerantand is therefore liquidtight. It is also gas-tight except for thepassages provided therein for the introduction and removal of gas in theoperation of the device. A liquid secondary refrigerant 16 is positionedwithin the lower container 44 and the quantity thereof is such as toleave a substantial head space thereabove within the container 44.

Particularly where the refrigerating unit is to be used in portableequipment it is desirable to provide a suitable number of baille plates16, 66 and 62 to reduce surging of the liquid. It has been founddesirable to keep the level of the liquid below that of the lowersurface of the up, permost baille plate 62. The baille plates 16, 6l and62 are so positioned as to permit free circu-l lation of the liquidwithin the container 44 and to permit free passage of gas through suchliq-l As shown in the drawing, the upper baille plate 62 is preferablyso positioned as to permit flow of gas around the edges thereof with aslittle restriction as possible and thus this baille plate may besupported by suitable angle brackets 64 secured to side walls ofthecontainer 44.

The exterior surfaces of the lower container 44 are preferably providedwith fins 66 to increase the area of the surfaces of the container. Thefins 66 may be formed from metallic angles welded or otherwise securedto the surfaces of the container 44.

Heat exchange between the solidified CO2 in the upper container 42 andthe secondary refrigerant in the lower container 44 is, except for minorconduction through the 'brackets 64 and walls 66 of the intermediatecontainer 66, solely effected by the passage of gaseous CO2 formed uponevaporation of the solidified C02. To this end one or more tubes orconduits 66 are provided. the upper ends 66 of which open into the uppercontainer 42. The conduits 66 are extended downwardly through the walls66 and through The horizontally disposed arms of a,449,oos

the top 92 of the lower container 44. 'Ihe con-l for a substantialdistance' upwardly of the conduit 99, All of the openingsi 94 should belocated below the level of the top of the secondary refrigerant 16. v v

'The top wall 92 of the lower container 44 also has formed therein oneor more openings 99 providing for the escape of gas leaving the surfaceofthe secondary refrigerant. It is preferred to provide conduits 99 ineach of such openings 99 which conduits extend upwardly to a pointadjacent the top of the refrigerating unit I6 and in proximity to thesurfaces of the upper container 42. Ordinarily a lconduit 99 will beprovided for at least two of the external vertical surfaces of the uppercontainer 42 and if desired, such a conduit may be provided for all fourvertical walls. The conduits 99 are open at their upper ends to permitescape of gas in a region which not only is in proximity to the upperexterior surfaces of the upper container 42, but also is the upperregion of the load-carrying compartment itself.

In order that the operation of the refrigera- `tion unit may beunderstood, it will be described first in general terms and then in aspecific embodiment. A -secondary refrigerant 16 is chosen having afreezing point such as to meet the requii'ements at hand. For example,=water may be chosen. The secondary refrigerant is placed in the lowercontainer 44 .and the quantity thereof is so chosen as to fill thecontainer 44 to approximately 75%-80% of its capacity. A quantity ofsolidified CO2 is placed in the upper' container 42 and the closure 56is secured. The unit I9 is then positioned Within the cabinet I0 and theclosure I 9 is closed.

Assuming 'that there is no food load in the compartment I2 and assumingthatthe air in said compartment is at a normal room temperature of 70F., it will be apparent that the solidified CO2 50 will begin to sublimeor evaporate and that the gaseous CO2 will soon begin to flow throughthe. conduit 89. When sufficient 'pressure has developed, the gaseousCO2 will begin to bubble upwardly through vthe secondary refrigerantwater 16. Some of the CO2 will be dissolved in the secondary refrigerantand the remainder will bubble completely through it and escape into thehead space above the baille l2 from which it will be discharged throughthe conduit or conduits 98. As theV gaseous CO2 passes through the water16, heat exchange occurs and the CO2 is relatively warm as it leaves theupper end of the conduit 98. It is still colder and heavier than theatmosphere ofthe compartment I2 and furthermore is discharged in a.region adjacent the relatively cold exterior surfaces of the uppercontainer 42. Thus the gaseous CO2 will descend along the exteriorsurfaces of the upper container 42, the intermediate container. 6'6 andthe finned lower container 44. This produces a positive scrubbingl ofsuch exterior surfaces and produces a positive circulation ofth'e'atmosphere in the compartment I2.

Such operation proceeds until the atmosphere has been considerablycooled and the temperature of the secondary refrigerant has been broughtdown substantially to the freezing point thereof.

In the meantime a portion of the moisture in the atmosphere lofcompartment I2 will have been deposited on the exterior surfaces of 'theupper container 42,111 the form of a layer of frost. Such frost layerwill build up quickly in view of the largely indirect heat transferbetween the walls of container 42 and the extremely cold solidified CO2therein. The4 frost layer serves to insulate the upper container 42,sharply reducing the rate of sublimation of the CO2 therein and alsoexposing the gaseous CO: emerging from conduit 98 to a much highertemperature than that encountered at first. `The atmosphere of thecompartment I2 is much cooler than at first thus further gqucing therate of sublimation of the solidified It will be recognized that theconditions just described have a strong tendency toward equilibrium andif it -were not for heat ,inflow through the cabinet I0 the secondaryrefrigerant would eventually freeze solid. The equilibrium is not tooprecarious, however, because of such heat inflow and because' of thetremendous amount of energy required to remove the latent heat of fusionof a liquid and bring about freezing thereofy when it is substantially.at its freezing point. As a consequence the secondary refrigerant 76serves as heat flywheel. The temperature' of the secondary refrigerantwill hover substantiallyat the freezing point thereof, irrespective ofrelatively great changes in the other conditions established at whichthe atmosphere of the compartment I2 is maintained by selection ofsecondary refrigerants having different f freezing points. When water isused and no food load is carried in the compartment, it has-been foundthat the atmosphere will be maintained at a temperature of about 34 to36 F.. assuming of course that the unit I6 is properly proportioned to.thecompartment III. The equilibrium established in a well insulatedempty compartment is rather delicate but this is not a condition whichwould be encountered in normal use ofthe device; A food load producesheat, different foods having different characteristics, as is wellknown; For example, string beans produce a relatively great amount ofheat and have been Aconsidered to be g difoult to ship underrefrigeration. .In the normal use of the present invention, the heatproduced by the food load plus the heat inflow in the cabinet will keepa unit I6 of proper size working at a relatively slow rate with nodanger of freezing up. It has been found that excellent results areachieved when the compartment temperature is established at about 10' or12 F. higher Ithan the freezing point of the secondary refrigerant.

When the unit is is in operation at its best efficiency. the secondaryrefrigerant will usually freeze and thaw to -a certain extent,` at mostto a point where some slush will float to the top. As pointed out abovethe apparatus must be designed to avoid solid freezing inasmuch as thiswould prevent bubbling of the gaseous CO2 through the openings willremain open. The plurality of openings is preferable to a singleopening, say

' merely the open end of the conduit itself, be-

cause of the tendency towardformation of ice at this point of nrstcontact between the cold CO2 gas and the liquid. When 'a plurality ofopenings is provided good circulation is assured -and the building up ofice at the openings is avoided.

' The circulation of the secondary refrigerant 16- within the lowercontainer u results in rapid heat transfer and in effect the interiorwalls of the container u are scrubbed in much the same manner as theexterior walls.

A specific embodiment of the invention comprises an outer cabinet Illmade of aluminum alloy, insulated with spun glass and having an interiorvolume of twelve cubic feet. The foraminous enclosure 38 andrefrigerating unit I6 therein occupy three cubic feet thus leaving ninecubic feet Afor storage of a commodity. Three and one-half gallons ofwater having one and threefourths pound of CaCl: dissolved therein isplaced in the lower container M as a secondary refrigerant. Thecontainer 44 is eighty percent full. If approxim-ately fifty pounds ofsolidified CO2 (about ya ten-inch cube) is placed in the upper containerand the compartment l2 is filled with string beans, for example, atemperature of from 35 F. t0 37'? F. will be maintained in thecompartment I2 for a period of about four days. The freezing point ofthe CaCl: solution used as a secondary refrigerant is 25 and as pointedout above a food load will lead to maintenance of a compartmenttemperature about 10 to 12 F. higher than such freezing point.

Obviously itwould be advantageous to precool the food load-to prolongthe effectiveness of a given quantity of solidified CO2. If the shipmentrequires more than the three or four day period for which the originalcharge is good the shipping container must he serviced.

Servicing of the shipping container may be carried out by removing theunit I6 therefrom and inserting an identical unit having a properquantity of solidified CO2 therein. Suitably located servicing depotsmay be established for this purpose. Alternatively, the shippingcontainer may be serviced merely by adding solidifled CO2` to the uppercontainer 42.

When a unit I8 is exhausted of its charge of solidified CO2 and warms upthe frost on the upper container 42 will melt, dripping into theintermediate container 66. Ordinarily this will not occur when the unitIi is positioned within a shipping container filled with a commodityinasmuch as it is contemplated that the units will be removed orserviced before exhaustion. However, the construction just describedwill prevent water damage t the contents of the shipping container intheevent defrosting should occur.

It is thus apparent that there has been disclosed a refrigerator andrefrigerating unit therefor which accomplishes the objects of theinvention. The description is presented in an illustrative rather thanin a limiting sense, and it 8 in the art within the scope of thefollowing claims. For example, any solidified material which exists as agas at ordinary atmospheric temperatures and pressures may besubstituted for the solidified CO2 if so desired.

Iclaim:

1. In a refrigerator having a load-carrying compartment for storage ofarticles in a refrigerated gaseous atmosphere, a substantially gas-tightcontainer for solidified CO2 located within said compartment, acontainer having a secondary refrigerant therein located within saidcompartment substantially out of direct heat-exchanging relationshipwith solidified CO2 in said firstnamed con-tainer, means to conductevaporated gaseous CO2 from said first-named container intoheat-exchanging relationship with said secondary refrigerant,and meansfor continuously discharging'said gaseous CO: after heat-exchange withsaid secondary refrigerant into an upper region of said refrigeratedcompartment whereby `to cause forced circulation of the atmosphere insaid compartment.

2. In a refrigerator having a load-carrying compartment for storage ofarticles in a refrigerated gaseous atmosphere. a substantially gastightcontainer for solidied CO2 located within said compartment, a containerhaving asecondary refrigerant 'therein located within said compartmentsubstantially out of direct heat-exchanging relationship With solidifiedCO2 in said rst-named container, means to conduct evaporated gaseous CO2from said first-named container into heat-exchanging relationship withsaid secondary refrigerant, and means for thereaf-ter conducting saidgaseous CO: to a zone in proximity with the upper exterior surfaces ofsaid first-named container.

. ship with said secondary refrigerant and means for thereafterconducting said gaseous CO: to a position for release into saidcompartment in a zone adjacent the upperexterior surfaces of saidfirst-named container whereby said relatively cool, relatively heavyreleased gaseous `lvCO: will descend along the exterior surfaces", ofsaid firstn'amed container and then along .the exterior surfaces of saidsecond-named container.

' 4. In a refrigerator having aiload-carrying compartment for storage ofarticles in a refrigerated gaseous atmosphere, a substantially gasftight container for solidified CO2, said container will be understoodthat modifications and variabeing located within and near the top ofsaid compartment. a second container having a secondary refrigeranttherein. said second container being spaced from said-first container tosubstantially prevent direct heat-exchange between said secondaryrefrigerant and solidified CO: in

tionship with said secondary'refrigerant, and

means for continuously discharging said gaseous C02 after heat-exchangewith said secondary refrigerant into said refrigerated compartment.

5. In a refrigerator having a load-carrying compartment for storage ofar-ticles in a refrigerated gaseous atmosphere. a substantially gastightcon-tainer for solidified CO2 located within said compartment, a secondcontainer. a secondary liquid refrigerant positioned wi-thin said seo--ond container, means for mountlngsaid second container in predeterminedspaced relationship with-said first,co'ntanier substantially to Vpreventdirect heat-exchange between said secondary refrigerant and solidifiedCO2 in said first container, at least one conduit connecting said firstcontainer` and said second container, said conduit having an openingvlocated below the level o'f the .top of said secondary refrigerantwhereby ievaporated gaseous CO2 will be conduc-ted from said firstcontainer to said second container and may bubble through saidsecond-ary refrigerant for heat-exchange therewith, and said secondcontainer having an opening formed therein above the level of saidsecondary refrigerant for the discharge from said second container ofsaid gaseous CO2 after it leaves said secondary refrigerant.

6. In a refrigerator having a load-carrying compartment for storage ofarticles in a refrigerated gaseous atmosphere, a substantially gastightcontainer for solidified CO: located within said compartment, a secondcontainer, a secondary liquid refrigerant positioned within said secondcontainer, means for mounting said second container in predeterminedspaced. relationship with said first container substantially to preventdirect heat-exchange between said secondary refrigerant and solidifiedCO2 in said first container, at least one conduit connecting said ilrstcontainer and said second con-tainer, said conduit terminating adjacentthe bottom ofsa'id secondcontainer and being provided with a pluralityof openings therein loca-ted within iand below .the level of the top ofsaid secondary' refrigerant whereby evaporated gaseous CO2 will beconducted from said first con-tainer to said second container and maybubble through said second-ary refrigerant for heat-exchange therewith,and said second container having an opening formed therein above .thelevel of said secondary refrigerant for the discharge from said secondcontainer of said gaseous CO2 after it leaves said secand being providedwith a plurality of vertically spaced openings therein located withinand below the level of the top of said secondary refrigerant wherebyevaporated gaseous CO2` will be conducted from said iirst container tosaid second container and may bubble through said secondary. refrigerantfor heat-exchange therewith, land at least one conduit opening into saidsecond container above, the level of said secondary refrigerant andextending upwardly to a regionv in l0 proximity with the exteriorsurface of Said lint container for discharge of said gaseous CO: intosaid region.

8. In a portable refrigerator having a loadcarrying compartment forstorage of articles in a refrigerated gaseous atmosphere, asubstantially gas-tight container for solidified CO: located within saidcompartment, a second container, a secondary liquid refrigerantpositioned within said second container, the quantity of said secondaryrefrigerant being such as to leave substantial v in proximity with theupper exterior surfaces of head space in said second container above thelevel of the top .of said secondary refrigerant. a plurality of bailleplates positioned in said second container to minimiz"e surging'of saidsecondary refrigerant during movement of said refrigerator,

means for mounting said second container in piredetermined spacedrelationship with said first container substantially to prevent directheatexchange vbetween said secondary refrigerant and solidified CO2 insaid first container, at least one conduit connecting said flrstcontainer and said second container, said conduit having at least oneopening located within and below the level of the top of said secondaryrefrigerant whereby evaporated gaseous CO2 will beconducted from saidfirst container to said second container and may bubble throughlsaidsecondary refrigerant for heat-exchange therewith, and said secondcontainer having an opening formed in the head space portion thereoffor' the discharge theresaid container.

10. In a refrigerator having a load-carrying compartment for storage ofarticles in a vrefrigerated, gaseous atmosphere, a substantiallygastig-ht container for solidified C0: located within said compartment,means for holding a supply of a liquid secondary refrigerant within saidcompartment in spaced relationship with said container substantially toprevent direct heat-exchange lbetween said secondary refrigerant andsolidified CO2 in said container, at least one conduit extending fromsaid container and having an opening located. below the level of the topof said secondary refrigerant from which evaporated gaseous CO2 maybubble through said secondary refrigerant for heat-exchange therewith,and means for discharging said gaseous CO2 after it leaves saidsecondary refrigerant into an upper region of said refrigeratedcompartment whereby to cause forced circulation -of the atmosphere insaid compartment.

11.. A refrigerated shipping container comprising a heat-insulated bodyhaving at least one closure movable for providing access to aloadcarrying compartment therein; a foraminous enclosure secured withinsaid compartment and defining a sub-compartment from which articles-stored in said load-carrying compartment are excluded by saidforaminous enclosure; at least n one closure movable for providingaccess to said ing unit arranged to utilize solidied CO2 as a 5 primary'refrigerant and having a secondary liquid refrigerant through whichgaseous CO2 may bubble upon evaporation of said solidified CO2, and saidrei'rigerating 4unit including means for continuouslyr discharging thegaseous CO2 leaving said secondary refrigerant into the loadcarryingcompartment to cause forced circulation of the atmosphere within saidcompartment.

ANDREW J. NICHOLAS.

l2 REFERENCES CITED The following references are of record in the illeof this patent:

UNITED STATES 'PATENTS Number Name vDate 1,825,068 Jones et al Sept. 29,1931 i 1,969,643 Fuchs et al. Aug. 7. 1934 10 2,142,569 Maranette Jan.3, 1939

